This invention relates to an improved process for the preparation of single-layered or multilayered molded articles from certain polyisocyanate polyaddition products by shaping such products under heat and pressure and to the molded articles thereby obtained.
According to published German patent application 3,733,756, molded articles can be prepared by thermoplastic shaping of granulates, shavings, or other small and very small particles of the kind obtained from the preparation and processing of polyisocyanate polyaddition products. According to published German patent application 3,809,524, complex structures and laminates can be prepared from such small particles and used either as such or in the form of semi-finished goods produced by a separate step.
It has been found, however, that disintegration may occur if materials differing substantially in their properties, for example, in their surface tension, are to be molded together in a single complex material. This problem can arise, for example, when using materials differing greatly in their hardness or materials formulated to be readily releasable from the mold and containing internal mold release agents. Such disintegration may also occur, for example, when lacquered and unlacquered materials are to be bonded together.
It is, therefore, an object of the present invention to provide an improved process by which all types of size-reduced polyisocyanate polyaddition products of the type mentioned below can be joined to form composite materials, regardless of their chemical composition and their physical properties.
It has surprisingly been found that the problem described above can be solved with the aid of certain processing auxiliaries described below.